Was anyone else's experience with GPT4o completely ruined after recent Update?

Same. I was lucky to get a full data export done in very reasonable time. I plan to check back in a month to see if it ‘stabilises’, given the latest related news:

Then I’ll see if it’s worthy also in light of the questionable roadmap regarding user tiers:

I suggest everyone: don’t get too attached to AI specific models and try alternatives like Claude and GH copilot. You might be surprised despite them missing some Chatgpt features.